As drilling mud is recirculated during drilling, debris from earth formations may damage sensitive downhole equipment. Filters used to collect the debris and thereby provide a way of removing the debris are known in the art. Often these filters will attach in single shouldered pipe such as described in U.S. Pat. No. 4,495,073 . The '073 patent discloses a mud screen for installation between any two selected ends of interconnected pipes comprising a supporting collar anchored in the selected threaded connection of the drill pipe string and a screen support mounted on such collar and secured thereto by one or more releasing devices. An apertured inverted conical screen is supported by the screen support in transverse relationship to the pipe bore. A bridging element is secured across the screen support and defines a mounting for an upstanding post which functions as a manual handle and also defines a fishing neck at its upper end for downhole retrieval.
U.S. Pat. No. 6,598,685 discloses another system for mounting a filter in a drill string. Disclosed is an apparatus comprising a cylindrical flange member having a first and second passage and a cylindrical sleeve having an internal fishing neck. An attachment pin attaches the flange member to the cylindrical sleeve. The apparatus further comprises a screen member attached to the cylindrical sleeve. In one embodiment, the first and second passages are disposed off-centered so that four bore holes are created. The attachment pin cooperates with a groove formed on the sleeve's outer diameter surface. The apparatus may further include a pulling tool. The pulling tool contains a plurality of dog members disposed about the mandrel, and a spring that urges the dog members into engagement with a protuberance on the mandrel. The apparatus further comprises a shear pin attaching the dog members to the mandrel and wherein the shear pin is disposed within a slot so that the dog members can move axially relative to the mandrel.
U.S. Pat. No. 6,769,484 discloses a downhole expandable bore liner and well screen filter assembly that has a perforated tubular base-pipe overlain with a self expanding filter-cover. A set of runners or bumpers extend the length of the outside of the filter-cover. A releaseable constriction mechanism holds the liner/filter assembly in a compressed configuration during insertion of the assembly down a well bore to facilitate insertion of the liner/filter assembly into its downhole position. Once positioned downhole in the well bore, the mechanism is released, and the liner/filter assembly takes its expanded or uncompressed configuration and interfaces with the walls of the well bore. In its uncompressed configuration, the liner/filter assembly can contact and press against the walls of the well bore, which contact serves to stabilize the assembly and to center it in the downhole well bore. The resilient and malleable nature of the filter material of the filter-cover can engage and at least partially fill and stabilize the irregularities in the formation wall of the well bore. Additionally, the resilient and malleable nature of the filter material of the filter-cover allows the assembly to utilize an expandable base-pipe in complement with the expandable filter material.